Author Archives: Paul Taylor

20 meters, 200mW & 12,000 miles: WSPR magic!

Weak Signal Propagation Reporter is a global radio propagation monitoring and reporting network comprised of thousands of low power beacons operating on the amateur radio bands. WSPR beacons can be detected from the lowest of Medium Wave frequencies (137kHz) all the way through the HF spectrum (all the bands from 160m to 10m are popular) to the VHF bands, 50 and 144MHz. WSPR receivers decode the tiny beacon packets and upload them to a central database, at WSPRNet.org, where anyone can literally ‘see’ the propagation paths that are currently open. Equally, you can go back and revisit the radio frequency propagation conditions during any previous time window. Running a WSPR beacon from your home allows you to ‘watch’ the propagation paths open, peak, and close each day under the influences of solar radiation, sunspots, and other ionospheric conditions. Arduinos and a few common accessory boards that can be had for tens of dollars make a beacon accessible to just about any experimenter (with an amateur radio license).

Continue reading
Tagged , , , , , , ,

Universal VFO Controller (ATMega328 & si5351)

This board is a universal radio project controller, with an ATMega328P(U) microcontroller and lots of options. The intention was for it to become a basic building block in transceivers, receivers, transmitters, signal generators, anywhere you need either a digital controller, one to three clocks, or both. The board has headers for the common si5351 breakout board, available from Adafruit or as a .CN clone, and a 16×2 HD7044 Liquid Crystal Display using the standard 14+2 parallel data header (+2 for backlight). It brings out all of the available digital IOs (D2..D13), analogue inputs (ADC) A0..A5), as well as headers for a 12V supply, and access to the regulated 7805 5v output, access to the LCD backlight in case you wish to take control of this in software, and an FTDI-compatible USB-to-serial programming board.

Continue reading
Tagged , ,

AGC for a Termination Insensitive Amplifier

For AGC controlled IF stages in receivers I have often chosen a 2 or 3 stage dual gate MOSFET strip, or a cascode arrangement with a bipolar and JFET pair.  These work well, have more than enough overall gain, and provide good AGC-controlled gain range.    I’ve also built a BiTX style transceiver (Andy G6LBQ’s design) with two Termination Insensitive Amplifier blocks. TIAs exhibit stable input and output impedance regardless of load, and work symmetrically (for receive and transmit) but are fixed gain. My BiTx receiver worked acceptably on 40m but was underpowered on 20m. Increasing the gain to make it more lively on 20m would have made it over-powered on 40m. You don’t have this problem when you have an AGC controlled IF.

Continue reading
Tagged , ,

SP-2B2C: A video series on the design and construction of a Dual-Band 2 Channel QRP CW rig

My radio projects to this point have typically involved a build and test effort, often spanning 3, 4 or even 6 months, culminating in one long, detailed blog post which was assembled over many months and a video that serves the dual purposes of showing and explaining the rig followed by an outing to one or more SOTA summits.

One consequence of this is that my video and blog output is quite low. Another is the resulting content is long, detailed, and not necessarily accessible to all readers or viewers. The concept/plan/build/test/box up and, finally, demonstrate approach is akin to building a house over a few years and publishing your account upon completion. So much of the story goes untold — old school thinking in 2021.

Continue reading
Tagged , ,

SP-8: a homebrew 28MHz SSB transceiver for a UR3LMZ 144MHz transverter

Ten meters or the 28MHz band is showing glimmers of life from sunspot cycle 25. Even so, its not an obvious choice if you want to build a portable SSB monobander and have lots of contacts. But 28MHz is the IF of choice for VHF and UHF transverters. After noticing the 6, 2 and 70cm transverters available on eBay from the workshop of UR3LMZ and the good reports from buyers, I cooked up the idea to build a 28MHz ‘transverter IF’ transceiver, to be paired with one or more VHF or UHF transverters.

Continue reading
Tagged , ,

SP-X, a pocket rig for the CW activator in a hurry!

I’ve long been interested in compact and fairly minimal SSB and CW rigs with good performance. I’m not into bells, whistles or menus. Menus are for restaurants! When hiking, walking or bouncing around summits I want to minimise things that are not absolutely necessary, things that can go wrong. Less is more when it comes to a transceiver for portable work.

Continue reading
Tagged , , , ,

Mt Feathertop (VK3/VE-002) 11th Jan 2021

Mt Feathertop (1,922 meters) is the second highest mountain in south eastern Australia (Victoria), and according to many commentators, the most picturesque and memorable. While Mt Bogong, the highest at 1,986 meters is a mammoth of bulk and stature, a bullock of a mountain with an ungainly rounded peak, Feathertop stands like a crafted blade fashioned out of a gigantic rocky plate tipped on its side aeons ago by the unfathomable forces that shaped our planet. So to stand on the top you must climb the supremely steep side from the valley below, or walk along its exposed knife-edge for 10 kilometers.

Continue reading
Tagged , ,

Digital SWR and Power Meter

This module is an analogue and digital SWR and power meter/monitor, designed to replace analogue SWR and power metering in an AM Transmitter project. Of equal importance was the ability to detect high SWR and raise an interlock (a control line) to inhibit transmitter power in the presence of unreasonably high SWR. I make no claim to either SWR or power accuracy; my version is an indicative tool and an interesting experiment, not an accurate test equipment, although it could be made into same with some skill and patience.

Continue reading
Tagged , , ,

Low-band AM Tx: Digital VFO/Controller

Lockdown has made 2020 a year unlike any other. Melburnians were dealt a long and painful period of isolation with a CoronaVirus second wave, from around July to September, still in force, and looking like continuing to (at least partially) keep us housebound for some months yet. Days merge together, work and leisure time is largely indistinguishable. People are rediscovering reading, knitting, and endlessly bingeing TV. Makers are melting solder and stringing wires in the air.

Some winter nights were passed dreaming up an AM transmitter, and this VFO module is the first piece of it. It is designed for use in a two-band AM transmitter capable of around 200 watts carrier power, but could easily be used for other projects, such as a transceiver, or a transmitter for CW or digital modes. This module provides a 5v square wave clock at 1.8MHz or 3.5MHz (or any frequency you desire up to 144MHz), and transmit control lines needed to sequence a transmitter. It also includes a few ‘nice to haves’ including a transmit timer, CW ident, over-beep (or any CW character such as di-da-dit or da-di-dah), and a sleep mode which dims the displays when idle.

Continue reading
Tagged , , ,

Ten Tec Model 1056 DC Receiver – is it any good, and what to do with it?

One of life’s simple pleasures is to rediscover something that bought you engagement and enjoyment in the past. And in COVID lockdown, stuck at home, it’s the perfect time to rummage through boxes in dark corners to sort, throw out, and rediscover old treasures. So it was that I came across this Ten Tec direct conversion receiver board, built around 20 years ago.

Continue reading
Tagged , ,
Shack of VK2KMI

Ham Radio Blog of VK2KMI

Ham Historian

A passionate amateur looks at Melbourne history

R.IT

My journey of repairing and recycling anything I put my hands on that I believe is still useful. Not just hardware, but including software with relevant content and issues in the field of Cyber Security, Vulnerability Scanning and Penetration Testing.

G4YDM Ham-Radio and SWL news

Radio craft, homebrew, QRP/SOTA, AM

VK3HN

Radio craft, homebrew, QRP/SOTA, AM

VK1DA.blog

Amateur radio experiences with VK1DA

Tj Lab

信号処理とラジオ

WA2MZE

Amateur Radio and unrelated technologies

Paul Gacek

W6PNG/M0SNA